Discussion summary: We discussed an interesting paper described as "Turning Jekyll into Hyde" in which Leung et al. discovered a new class of compounds termed ACPs for activators of self-compartmentalizing proteases. Five lead compounds were identified out of a high-throughput screen using a fluorescence assay based on the degradation of fluorescein isothiocyanate-labeled casein, an unfolded protein which is a ClpP substrate. These compounds act by stabilizing the tetradecamer form of ClpP and allowing unregulated degradation of many bacterial proteins. Normally, ClpP requires a AAA+ ATPase partner to unfold substrate proteins and thread them into the chamber for degradation. However, ClpP can be activated by acyldepsipeptides (ADEPs) which open its pores, allowing larger proteins to enter and be degraded. The ACPs, and an optimized compound based on these discovered scaffolds, have the same modes of action. (Leung et al., Chem. Biol. 18, 1167-1178, 2011).

Points that were discussed:

The meaning of B-score for high-throughput screening assays and how the ACP lead compounds were selected - additional screening was involved after first identifying the compounds.

ACP analogues with activity equal to ADEPs were identified.

Discussed procedures for ITC experiments and the meaning of the parameters - fixing n vs. allowing n to vary

Comparing the N-terminal truncation mutant vs the wildtype protein

Meaning of bactericidal vs. antibiotic

Does mutation of the H and C pocket keep the native oligomeric state? - these mutants retain native peptidase activity.